/lib/partman/check.d/10check_swap is in ubiquity 2.10.16.
This file is owned by root:root, with mode 0o755.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58  | #!/bin/sh
. /lib/partman/lib/base.sh
swap=false
for dev in $DEVICES/*; do
	[ -d "$dev" ] || continue
	cd $dev
	partitions=
	open_dialog PARTITIONS
	while { read_line num id size type fs path name; [ "$id" ]; }; do
		[ "$fs" != free ] || continue
		partitions="$partitions $id,$num"
	done
	close_dialog
	for part in $partitions; do
		id=${part%,*}
		num=${part#*,}
		[ -f $id/method ] || continue
		method=$(cat $id/method)
		if [ "$method" = swap ]; then
			swap=:
		fi
		[ ! -f $id/format ] || continue
		if [ "$method" = swap ]; then
			log "Check the swap space in $dev/$id"
			template=partman-basicfilesystems/progress_swap_checking
			db_subst $template PARTITION "$num"
			db_subst $template DEVICE $(humandev $(cat device))
			name_progress_bar $template
			open_dialog CHECK_FILE_SYSTEM $id
			read_line status
			close_dialog
			if [ "$status" != good ]; then
				db_subst partman-basicfilesystems/swap_check_failed PARTITION "$num"
				db_subst partman-basicfilesystems/swap_check_failed DEVICE $(humandev $(cat device))
				db_set partman-basicfilesystems/swap_check_failed true
				db_input critical partman-basicfilesystems/swap_check_failed || true
				db_go || true
				db_get partman-basicfilesystems/swap_check_failed
				if [ "$RET" = true ]; then
					exit 1
				fi
			fi
		fi
	done
done
if ! $swap; then
	db_input critical partman-basicfilesystems/no_swap || true
	db_go || true
	db_get partman-basicfilesystems/no_swap
	if [ "$RET" = true ]; then
		exit 1
	fi
fi
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